Magneto rotor



Oct. 11, 1938.

H. G. cox

MAGNETO ROTOR Filed Sept. 26, 1934 IN V EN TOR.

WITNESS Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE 3 Claims.

? tact with the magnets by centrifugal force from the rotation of the rotor; to provide a rotor wherein the magnets are of the simplest bar type but have high magnetic efficiency because of improved means for both increasing the area of magnetic contact and intimately cohesively uniting the magnets to the magnetic bridge between them; and to provide improved means for rotatably supporting a plurality of bar magnets.

An illustrative embodiment of this invention is shown in the accompanying drawing, wherein:

Fig. 1 is an axial section of the improved rotor; the magnets and the drive shaft being shown in elevation.

Fig. 2 is a side elevation of the rotor.

Figs. 3 and 4 are transverse sections taken respectively on the lines 3-3, and 4-4 of Fig. l.

Inasmuch as this invention relates particularly to the rotor, the other parts of the magneto have been omitted from the drawing.

In the form shown, the improved rotor comprises a drive shaft I and four straight bar permanent magnets 2 or two pairs which are carried by the drive shaft and which are arranged side by side in substantially parallel spaced relation to another. In order to balance the rotor, the magnets are relatively arranged so as to be equi-distant from the axis of the drive shaft.

At one end the magnets are firmly held by a ferrous metal magnetic bridge 3, preferably melted and cast around the periphery of the magnets, which after shrinking in cooling gives an extremely intimate cohesion of the bridge metal with the magnets forming a continuous homogeneous mass, resulting in converting each pair of magnets into an integral inseparable one-piece substantially U-shaped magnet, and providing an exceptionally effective magnetic joint. And since the bridge encircles the periphery of the magnets, and runs up the sides as much as desired, a much greater area for the intimate cohesion and unification of the magnets and bridge is available and a greater magnetic flow obtained than where the same magnets contact the bridge only by their ends, as disclosed in prior art patents.

glass.

A cold pressed fit, or hot shrunk fit of the magnets into the bridge is the next best magnetic joint to the cast fit, but both cost more to make than the cast fit, which is very quickly and cheaply made, especially when die cast. 5

In the manufacture of single piece U-shaped magnets it is the practice to heat the lengths of magnet steel before magnetization to 1700 degrees F., then bend such lengths into U shape, and deposit them in a box of ground mica or lime to permit them to cool slowly and thus ease the strains set up in the steel by the act of bending, otherwise if it is attempted to bend and harden the lengths in the same heat by quenching them the parts might crack in a manner similar to When the bars have cooled they are then heated to 1500 degrees F. and quenched in oil or water, after which they are magnetized. In carrying out my invention, therefore, it will be apparent that by casting an iron bridge around the peripheries of the ends of the magnet bars in a steel mould such bars will become heated to a limited temperature only, probably not more than four or five hundred degrees, which, as will be understood is not by any means nearly as 2! severe on the bars as the temperature of 1700 degrees above explained, and which bars it is unnecessary to subject to strains of bending. After the iron bridge cools the bridge and magnet bars assembled therewith are heated to 1500 degrees, and then quenched in oil or water, when the assemblage is in condition for the permanent magnetic charge; and it will be understood that this second heating of the iron bridge is highly beneficial to it by easing any strains which might 85 otherwise cause it to crack eventually.

The opposite ends of the magnets from the bridge are supported by a non-magnetic drive plate 4 encircling their sides, but not abutting their ends.

The magnetic bridge and the non-magnetic drive plate are mounted on and keyed to a drive shaft which rotates the rotor assembly.

Located adjacent to the non-magnetic drive plate are two sets of magnetizable laminae 5 which respectively bridge the like poles of the magnets. These laminae consist of alternately arranged stampings 6 and I having openings 8 and 9 respectively, for receiving the legs oi the magnets. In order to prevent magnetic short circuiting these stampings are slit as shown at H) and II. If the laminae are not firmly bound to the magnets, they will be thrown outwardly by centrifugal force out of metal to metal contact with the magnets, during rotation of the rotor,

thus breaking a good magnetic joint and introducing another air gap in the circuit. Also since the air gap between the revolving rotor and the stationary pole pieces of a stator with which it cooperates is only .002 to .005 inch thick the laminae may actually rub on the pole pieces and destroy themselves.

To prevent such outward throwing, the laminae of this improved rotor are firmly bound to the magnets by four dowel rods l2, which extend through apertures l3 and M in the stampings 6 and 1 respectively. The apertures l3 of the stampings 6 are slightly staggered with respect to the apertures M of the stampings 1, so

that when the dowel rods are driven through the.

apertures, certain portions of the stampings will contract to firmly grip the magnets.

A rotor of this improved construction is highly efiicient, is proof against vibration, is cheaply made and quickly assembled.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that certain details of the construction shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.

I claim:

1. 'A magneto rotor comprising a plurality of permanent magnets arranged in substantially parallel spaced relation, means for supporting the magnets in spaced relation, a clamp embrac ing the peripheries of one end of the magnets and cohesively united therewith, a plurality of magnetic laminae bridging the like poles respectively of said magnets and having openings for receiving said magnets, said laminae having apertures therein, the apertures of certain of said laminae being staggered withrespect to the apertures of other laminae, and dowel rods extending through said apertures for binding said 1aminae to said magnets.

2. A magneto rotor comprising a plurality of permanent magnets arranged in substantially parallel spaced relation, means for supporting the magnets in spaced relation, a clamp embracing the peripheries of one end of the magnets and cohesively united therewith, a plurality of magnetic laminae bridging the like poles respectively of said magnets and having openings for receiving said magnets, portions of said laminae being slit adjacent said openings to prevent magnetic short circuiting around the poles, said laminae having apertures therein, the apertures of certain of said laminae being staggered with respect to the apertures 'of other laminae, and

. dowel rods extending through said apertures for binding said laminae to said magnets.

3. A magneto rotor comprising a plurality of permanent magnets arranged in substantially parallel spaced relation, means for supporting the magnets in spaced relation, a clamp embracing the peripheries of one end of the magnets and cohesively united therewith, a plurality of magnetic laminae bridging the like poles respectively of said magnets and having openings for receiving said magnets, portions of said laminae being slit adjacent said openings to prevent magnetic short circuiting around the poles, said laminae having apertures therein, said apertures being staggered axially, and dowel rods extending through said apertures for binding said laminae to said magnets, said dowel rods having headson one end and riveted to the drive plate on the other end to prevent the laminae moving axially.

HENRY G. COX. 

